This invention relates generally to afterburners, and, more particularly to a partial swirl augmentor for a turbofan engine.
It is well known in the aircraft gas turbine art to provide thrust augmentation by burning additional fuel in an afterburner located downstream of the engine turbine. The afterburner generally includes a means for dispersing a main flow of fuel together with a flameholder to which the flame may attach. The flameholder reduces locally the velocity of the gas stream in order to sustain the flame which would otherwise blow out. One well known type of flameholder comprises two concentric flame rings arranged to diverge from each other in a downstream direction. The main flow of fuel is dispersed in a manner that allows fuel droplets to impinge upon the outside diverging surfaces of the flameholder wherein the afterburning flame attaches to the trailing edges of the flame rings.
In order to provide for positive and uniform lightoff of the afterburner during all modes of flight operation, pilot fuel may be introduced and sparked to ignite by means of a point source igniter. The pilot flame in turn operates to ignite the main fuel droplets. It is well known to introduce the pilot fuel to the afterburner by means of discrete jets situated around the flameholder. The pilot fuel jets are generally located intermediate the flame rings such that each pilot jet receives gas flow from the turbine exhaust through an individual inlet opening in the leading edge of the flameholder.
Generally state-of-the-art afterburners leave much to be desired since they do not permit swirling airflow in the afterburner because high velocities will exist over the flameholder causing both blow-out and decreased engine thrust due to high flameholder pressure loss.